Quote:
Originally Posted by FrancoRodriguez
Just wondering, what's your 70-200? Canon/Nikon/Sony? I've got the nikkor f4 version and an 071. Haven't tried them together yet (actually haven't tried any lens with it). What spacing did you use? Does it matter if it's off the recommended backfocus by 1 mm or so?
Thanks
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My lens is the Canon 70-200 IS L for EF mount. DSLR lenses have substantially more backfocus for use with mono cameras than their mirrorless counterparts, which have smaller than half of the flange focal distance of DSLRs, typically.
I’d recommend hitting the backfocus spot on if you can - use thin metal/plastic rings to nail the right spacing as necessary. The lenses are designed to tight tolerances, so deviation from the ideal may result in undesirable aberrations that don’t show (or are minimised) at the intended backfocus. It’ll also throw out the focal point from the gauge on the lens.
Also, don’t forget that if you’re using a UV/IR cut (or any other filter) in front of the sensor, that will throw the focal plane further back. I think the figure is of the order of 1/3mm shift per filter thickness.
Hope that helps...